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Claude Agent Skills:

🤖 Agent Skills: Comprehensive Guide

🤖 Comparative Analysis of Progressive Disclosure in Claude Agent Skills and Model Context Protocol (MCP) Tool-Based Approaches

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1. Overview

Agent Skills are modular capabilities that extend Claude's functionality. Each Skill packages instructions, metadata, and optional resources (scripts, templates) that Claude uses automatically when relevant.

Skills are reusable, filesystem-based resources that provide Claude with domain-specific expertise: workflows, context, and best practices that transform general-purpose agents into specialists. Unlike prompts (conversation-level instructions for one-off tasks), Skills load on-demand and eliminate the need to repeatedly provide the same guidance across multiple conversations.

Key Benefits

• Specialize Claude: Tailor capabilities for domain-specific tasks
• Reduce repetition: Create once, use automatically
• Compose capabilities: Combine Skills to build complex workflows

Note: For a deep dive into the architecture and real-world applications of Agent Skills, read the Anthropic engineering blog: "Equipping agents for the real world with Agent Skills".

How Skills Work

Skills leverage Claude's VM environment to provide capabilities beyond what's possible with prompts alone. Claude operates in a virtual machine with filesystem access, allowing Skills to exist as directories containing instructions, executable code, and reference materials.

This filesystem-based architecture enables progressive disclosure: Claude loads information in stages as needed, rather than consuming context upfront.

Three Levels of Loading

Level 1: Metadata (Always loaded) The Skill's YAML frontmatter provides discovery information. Claude loads this at startup and includes it in the system prompt.

• Cost: ~100 tokens per Skill.
• Content: name and description.

Level 2: Instructions (Loaded when triggered) When you request something that matches a Skill's description, Claude reads the main SKILL.md file from the filesystem via bash. Only then does this content enter the context window.

• Cost: Under 5k tokens (recommended).
• Content: Workflows, best practices, and guidance.

Level 3: Resources and Code (Loaded as needed) Skills can bundle additional materials like scripts, databases, or large reference files. Claude accesses these files only when referenced in the instructions or needed for a task.